1. Field of the Invention
This invention relates to a micro-processing method for forming an extremely small electroconductive region surrounded by a non-electroconductive region on a non-electroconductive substrate and, more particularly, it relates to a micro-processing method using a scanning probe microscope provided with a probe having a micro-aperture for irradiation of light.
2.Related Background Art
The invention of the scanning tunneling microscope (hereinafter referred to as STM) made it possible to observe the surface of the specimen with an enhanced degree of resolution such that the observer can visually perceive atoms [G. Binnig et al., Phys. Rev. Lett. 49, 57(1982)]. In other words, a real space image of the specimen can be obtained at the atomic or molecular level. A scanning tunneling microscope is designed to scan the surface of an electroconductive specimen by controlling the distance between the probe electrode of the microscope and the specimen in such a way that the tunneling current may be held to a constant level. Then, information on the electron cloud of the surface of the specimen and the profile of the specimen can be obtained from the control signal used for controlling the operation. Such information normally contains data on details of the specimen expressed in terms of sub-nanometer.
The atomic force microscope (hereinafter referred to as AFM) is also a recent invention that can be used to observe the surface of the specimen with an enhanced degree of resolution. The AFM can be used to observe details of the surface of a non-electroconductive object in terms of sub-nanometer.
Microscopes such as STMs and AFMs that are designed to two-dimensionally scan the surface of the specimen by means of a probe in order to obtain physical information on the surface of the specimen on the basis of the interaction of the probe and the surface of the specimen are generally referred to as scanning probe microscopes (SPM). The SPM is attracting attention as means for observing the surface of an object with an enhanced degree of resolution.
It is now possible to carry out a micro-processing operation on a material at the atomic level of atoms by applying the principle underlying the SPM.
Japanese Patent Application Laid-Open Nos. 63-161552 and 63-161553 describe a technology for raising the electroconductivity of an insulation film by applying a voltage to the film, utilizing the STM technology.
With the disclosed technology, an extremely small region of the order of nanometers having an enhanced electroconductivity can be produced in a film.
Generally, it is possible to prepare a device component showing a quantum effect by confining electrons within a micro-region of the order of sub-microns.
For example, a structure called a quantum dot that shows an electron confinement effect can be obtained by forming a spherical or cubic electroconductive region of the order of several nanometers to tens of several nanometers and enclosing it with a non-electroconductive region.
Similarly, a structure called a quantum wire can be obtained by forming a rod-shaped electroconductive region having a diameter of the order of several nanometers to tens of several nanometers and enclosing it with a non-electroconductive region. Thus, the technique of forming a structure adapted to confine electrons within an extremely small region plays a very important role in the process of preparing a device having a quantum effect.
However, with the technology disclosed by Japanese Patent Application Laid-Open Nos. 63-161552 and 63-161553, electrons cannot successfully be confined within an extremely small region because the region showing an enhanced electroconductivity is electrically connected to the substrate electrode.